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Plasma Sci. Technol.  
  Plasma Sci. Technol.--2015, 17 (7)   Published: 04 June 2015
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Basic Plasma Phenomena

Experimental Study on Light Flash Radiant Intensity Generated by Strong Shock 2A12 Aluminum Plate

TANG Enling (唐恩凌) 1,ZHANG Lijiao (张立佼) 1,ZHANG Qingming (张庆明) 2,et al.
Plasma Sci. Technol. 2015, 17 (7): 529-533 ;  doi: 10.1088/1009-0630/17/7/01
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Show Abstract ( 238 )

In order to study the light flash radiant intensity produced by strong shock on a 2A12 aluminum target at the same projectile incidence angles and different shock velocities, experimental measurements were conducted for light flash phenomena of a 2A12 aluminum projectile impacting a 2A12 aluminum target under the conditions of different impact velocity and the same projectile incidence angles of 45 ? by using an optical pyrometer measurement system and a two-stage light gas gun loading system. Experimental results show that the peak values of the light flash radiant intensity for the wavelength of 550 nm are largest in the wavelength ranges of 600 nm, 650 nm and 700 nm when a 2A12 aluminum projectile impacts a double-layer 2A12 aluminum plate in the present experimental conditions.

Magnetically Confined Plasma

Ion Heating from Nonlinear Landau Damping of High Mode Number Toroidal Alfvén Eigenmodes Hot!

T. S. HAHM
Plasma Sci. Technol. 2015, 17 (7): 534-538 ;  doi: 10.1088/1009-0630/16/7/02
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Bulk ion heating rate from nonlinear Landau damping of high mode number Toroidal Alfv´ en Eigenmodes (TAEs) is calculated in the frame work of weak turbulence theory. The heating rate is lower than the nonlinear spectral transfer rate to more stable modes, but relatively insensitive to the details of linear damping mechanisms.

On the Transition Regime of Nonlinear Error Field Penetration in Toroidal Plasmas

WANG Huihui (王辉辉) 1,2,WANG Zhengxiong (王正汹) 1,DING Yonghua (丁永华) 3,et al.
Plasma Sci. Technol. 2015, 17 (7): 539-544 ;  doi: 10.1088/1009-0630/17/7/03
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The error field penetration is numerically studied in the frame of the visco-resistive magnetohydrodynamics (MHD) model. A transition scaling is obtained to link the Rutherford and Waelbroeck regimes in the nonlinear phase of error field penetration process. Furthermore, a transition density scaling of

[b r /B T ] crit ∼ n1/2e is obtained in accord with recent experimental observations in the J-TEXT tokamak.

Calculation of Neutral Beam Injected Torque and Its Effective Tangency Major Radius for EAST

WU Xingquan (伍兴权), WAN Baonian (万宝年), LYU Bo (吕波), et al.
Plasma Sci. Technol. 2015, 17 (7): 545-551 ;  doi: 10.1088/1009-0630/17/7/04
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Toroidal rotation has been recognized to have significant effects on the transport and magnetohydrodynamic (MHD) stability of tokamak plasmas. Neutral beam injection (NBI) is the most effective rotation generation method on current tokamak devices. To estimate the effective injected torque of the first neutral beam injection system on EAST, a simplified analytic method was derived. Calculated beam torque values were validated by those obtained from the NUBEAM code simulation. According to the results, for the collisional torque, the effective tangential radius for torque deposition is close to the beam tangency major radius. However, due to the dielectric property of tokamak plasma, the equivalent tangency major radius of the  J ×  B torque is equal to the average major radius of the magnetic flux surface. The results will be useful for the research of toroidal momentum confinement and the experimental analysis of momentum transport related with NBI on EAST.

Inertially Confined Plasma

Fusion of Multi-Pinched Plasma Beams Converging with Spatial Symmetry

MIAO Feng (苗峰) 1,ZHENG Xianjun (?曾宪俊) 2,DENG Baiquan (邓柏权)3
Plasma Sci. Technol. 2015, 17 (7): 552-559 ;  doi: 10.1088/1009-0630/17/7/05
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Show Abstract ( 335 )

Fusion reactions can be achieved by using deuterium from sea water as the fuel. The amount of deuterium in one gallon of sea water contains energy equivalent to three hundred gallons of gasoline. Satisfactory conditions of plasma temperature and density necessary to initiate fusion have been achieved in various research facilities. However, the confinement time is not sufficient for ignition due to plasma instabilities. Here we show that fatal plasma instabilities could be suppressed by the ingenious arrangement of multi-pinched plasma beams converging symmetrically in space based on the minimization principle of plasma potential energy. Confirmation tests are proposed using tiny wires containing deuterium. If successful, the results could lead to a feasible approach to obtaining commercial fusion power from sea water, hence without the need to use expensive and radioactive tritium as the fuel.

Low Temperature Plasma

Effects of Tailed Pulse-Bias on Ion Energy Distributions and Charging Effects on Insulating Substrates

LIU Zeng (刘增), DAI Zhongling (戴忠玲), HE Caiqiang (贺才强),WANG Younian (王友年)
Plasma Sci. Technol. 2015, 17 (7): 560-566 ;  doi: 10.1088/1009-0630/17/7/06
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A hybrid sheath model, including a fluid model and a Monte Carlo (MC) method, is proposed to study ion energy distributions (IEDs) driven by a radiofrequency (RF) with a tailed pulse-bias on an insulating substrate, where a charging effect is obviously caused by the ions accumulated. This surface charging effect will significantly affect the IEDs on the insulating substrate. In this paper, a voltage compensation method is employed to eliminate the charging effect by making the pulse-bias waveform have a certain gradient. Furthermore, we investigate the IEDs under the condition of different pulse-bias duty ratios, waveforms, amplitudes, and cycle proportions. It is found that the parameters of the pulsed source can effectively modulate the IEDs on the insulating substrate and the charging effect, and more desired IEDs are obtained by using the voltage compensation method with modulations of pulse parameters.

Plasma Technology

Atmospheric Pressure Plasma Processing of Fused Silica in Different Discharge Modes

LI Na (李娜), XIN Qiang (辛强), ZHANG Peng (张鹏), WANG Bo (王波)
Plasma Sci. Technol. 2015, 17 (7): 567-573 ;  doi: 10.1088/1009-0630/17/7/07
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One of the major advantages of utilizing atmospheric pressure plasma processing (APPP) technology to fabricate ultra-precision optics is that there is no subsurface damage during the process. In APPP, the removal footprint and removal rate are critical to the capability and efficiency of the figuring of the optical surface. In this paper, an atmospheric plasma torch, which can work in both remote mode and contact mode, is presented. The footprints and the removal rates of both modes are compared by profilometer measurements. The influences of process recipes and substrate thickness for both modes are investigated through a series of experiments. When the substrate is thinner than 12 mm, the removal rate in contact mode is higher. However, the removal rate and width of the footprint decrease dramatically as the substrate thickness increases in contact mode.

Cytotoxicity of Boron-Doped Nanocrystalline Diamond Films Prepared by Microwave Plasma Chemical Vapor Deposition

LIU Dan (刘丹) 1,GOU Li (芶立) 1,2,RAN Junguo (冉均国) 1,ZHU Hong (朱虹) 1,et al.
Plasma Sci. Technol. 2015, 17 (7): 574-578 ;  doi: 10.1088/1009-0630/17/7/08
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Boron-doped nanocrystalline diamond (NCD) exhibits extraordinary mechanical properties and chemical stability, making it highly suitable for biomedical applications. For implant materials, the impact of boron-doped NCD films on the character of cell growth (i.e., adhesion, proliferation) is very important. Boron-doped NCD films with resistivity of 10 −2 Ω·cm were grown on Si substrates by the microwave plasma chemical vapor deposition (MPCVD) pro- cess with H 2 bubbled B 2 O 3 . The crystal structure, diamond character, surface morphology, and surface roughness of the boron-doped NCD films were analyzed using different characterization methods, such as X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The contact potential difference and possible boron distribution within the film were studied with a scanning kelvin force microscope (SKFM). The cy- totoxicity of films was studied by in vitro tests, including fluorescence microscopy, SEM and MTT assay. Results indicated that the surface roughness value of NCD films was 56.6 nm and boron was probably accumulated at the boundaries between diamond agglomerates. MG-63 cells adhered well and exhibited a significant growth on the surface of films, suggesting that the boron-doped NCD films were non-toxic to cells.

Synthesis of Diamond Nanoplatelets/Carbon Nanowalls on Graphite Substrate by MPCVD

ZHANG Wei (张玮) 1,2,LYU Jilei (吕继磊) 1,LIN Xiaoqi (林小琪) 1,2,et al.
Plasma Sci. Technol. 2015, 17 (7): 579-582 ;  doi: 10.1088/1009-0630/17/7/09
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The films composed of carbon nanowalls and diamond nanoplatelets, respectively, can be simultaneously formed on graphite substrate by controlling the hydrogen etching rate during microwave plasma chemical vapor deposition. To modulate the etching rate, two kinds of substrate design were used: a bare graphite plate and a graphite groove covered with a single crystal diamond sheet. After deposition at 1200 ? C for 3 hours, we find that dense diamond nanoplatelets were grown on the bare graphite, whereas carbon nanowalls were formed on the grooved surface, indicating that not only reaction temperature but also etching behavior is a key factor for nanostructure formation.

Effect of Frequency and Power of Bias Applied to Substrate on Plasma Property of Very-High-Frequency Magnetron Sputtering

LIU Yi (刘毅) 1,YE Chao (叶超) 1,2,HE Haijie (何海杰) 1,WANG Xiangying (王响英) 3
Plasma Sci. Technol. 2015, 17 (7): 583-588 ;  doi: 10.1088/1009-0630/17/7/10
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The effect of the frequency and power of the bias applied to the substrate on plasma properties in 60 MHz (VHF) magnetron sputtering was investigated. The plasma properties in- clude the ion velocity distribution function (IVDF), electron energy probability function (EEPF), electron density n e , ion flux Γ i , and effective electron temperature T eff . These parameters were measured by a retarding field energy analyzer and a Langmuir probe in the 60 MHz magnetron sputtering, assisted with 13.56 MHz or 27.12 MHz substrate bias. The 13.56 MHz substrate bias led to broadening and multi-peaks IVDFs, Maxwellian EEPFs, as well as high electron density, ion flux, and low electron temperature. The 27.12 MHz substrate bias led to a further increase of electron density and ion flux, but made the IVDFs narrow. Therefore, the frequency of the substrate bias was a possible way to control the plasma properties in VHF magnetron sputtering.

Chemical Analysis of NO 2 Removal Under Different Reduced Electric Fields

A. HADDOUCHE, M. LEMERINI
Plasma Sci. Technol. 2015, 17 (7): 589-594 ;  doi: 10.1088/1009-0630/17/7/11
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This work presents a chemical kinetic analysis of different species involved in nitrogen-oxygen mixed gas induced by stationary corona discharge at room temperature and at- mospheric pressure. This study takes into account twenty different chemical species participating in one hundred and seventy selected chemical reactions. The reaction rate coefficients are taken from the literature, and the density is analyzed by the continuity equation without the diffusion term.

A large number of investigations considered the removal of NO x showing the effects of N, O and O 3 radicals. The aim of the present simulation is to complete these studies by analysing various plasma species under different reduced electric fields in the range of 100-200 Td (1 Td=10 −21 V·m 2 ). In particular, we analyze the time evolution of depopulation (10 −9 -10 −3 s) of NO x . We have found that the depopulation rate of NO and NO 2 is substantially affected by the rise of reduced electric field as it grows from 100 Td to 200 Td. This allows us to ascertain the important role played by the reduced electric field.

Fusion Engineering

Exposure of Equal-Channel Angular Extruded Tungsten to Deuterium Plasma

LIU Feng (刘凤) 1,XU Yuping (徐玉平) 1,ZHOU Haishan (周海山) 1,et al.
Plasma Sci. Technol. 2015, 17 (7): 595-600 ;  doi: 10.1088/1009-0630/16/17/7/12
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Surface morphology and deuterium retention in ultrafine-grained tungsten fabricated by equal-channel angular pressing (ECAP) have been examined after exposure to a low energy, high-flux deuterium (D) plasma at fluences of 3×10 24 D/m 2 and 1×10 25 D/m 2 in a temperature range of 100 ? C-150 ? C. The methods used were scanning electron microscopy (SEM) and thermal desorption spectroscopy (TDS). Sparse and small blisters (∼0.1 μm) were observed by SEM after D plasma irradiation on every irradiated surface; yet they did not exhibit significant structure or plasma fluence dependence. Larger blisters or protrusions appeared after subsequent TDS heating up to 1000 ? C. The TDS results showed a single D desorption peak at ∼220 ? C for all samples and the D retention increased with increasing numbers of extrusion passes, i.e., the decrease of grain sizes. The increased D retention in this low temperature range should be attributed to the faster diffusion of D along the larger volume fraction of grain boundaries introduced by ECAP.

Development of Distributed Control System for Neutral Beam Injector on EAST

SHENG Peng (盛鹏), HU Chundong (胡纯栋), CUI Qinglong (崔庆龙), et al.
Plasma Sci. Technol. 2015, 17 (7): 601-606 ;  doi: 10.1088/1009-0630/17/7/13
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A distributed control system of Neutral Beam Injector (NBI) on the Experimental Advanced Superconducting Tokamak (EAST-NBI) is briefly presented in this paper. The control system is developed in accordance with the experimental operational characteristics of the EAST- NBI. The NBI control system (NBICS), which is based on the computer network technologies and classified according to the control levels, consists of three levels: a remote monitoring layer, a server control layer, and a field control layer. The 3-layer architecture is capable of extending the system functions and upgrading devices. The timing system provides the reference clock of the synchronization and interlock for the EAST-NBI system. An interlock system ensures the safety of the experiment operators and field devices. Both of the ion sources of the beamline are designed to operate independently. This lays an important foundation for developing a control system for the second beamline on EAST. Experimental results demonstrate that the NBICS meets functional requirements of the EAST-NBI control, and makes experimental operations visual and automatic.

Neutronic Calculation Analysis for CN HCCB TBM-Set

CAO Qixiang (曹启祥), ZHAO Fengchao (赵奉超), ZHAO Zhou (赵周), et al.
Plasma Sci. Technol. 2015, 17 (7): 607-611 ;  doi: 10.1088/1009-0630/17/7/14
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Using the Monte Carlo transport code MCNP, neutronic calculation analysis for China helium cooled ceramic breeder test blanket module (CN HCCB TBM) and the associated shield block (together called TBM-set) has been carried out based on the latest design of HCCB TBM-set and C-lite model. Key nuclear responses of HCCB TBM-set, such as the neutron flux, tritium production rate, nuclear heating and radiation damage, have been obtained and discussed. These nuclear performance data can be used as the basic input data for other analyses of HCCB TBM-set, such as thermal-hydraulics, thermal-mechanics and safety analysis.

R&D Activities of Joint Manufacture for ITER Poloidal Field Coil

YAO Yao (姚尧), SONG Yuntao (宋云涛), HUANG Xiongyi (黄雄一), et al.
Plasma Sci. Technol. 2015, 17 (7): 612-616 ;  doi: 10.1088/1009-0630/17/7/15
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Electrical joints are critical components of the PF coil in the tokamak, serving as an electric and coolant transfer between adjacent conductors. The technologies and tooling used for joint manufacture are great challenges in coil fabrication, including termination box and cover manufacturing, jacket removal of the conductor, petals drawing apart and reformation, nickel coating removal and tin plating on the cable, compaction of the cable into the termination, final machining of the termination, etc. This paper mainly focuses on the solution of technical issues, based on previous R&D activities of joint. Meanwhile, a detailed manufacture plan has been confirmed. The technologies and tooling also can be used as reference for the electrical joint manufacture for PF coils and other large-scale coils.

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